1. Field of the Invention
This invention generally relates to a container which provides for the collection of a sample of a biological fluid, the centrifugation of the fluid in the case of serum, and accurate dispensing of micro amounts of the fluid for testing, all without requiring the pouring of the fluid into a variety of separate containers. More specifically, it relates to improved devices for providing the combined functions of serum separation and dispensing.
2. State of the Prior Art
The most common conventional method of providing biological fluid such as blood serum for clinical analysis utilizes a plurality of containers en route to the actual test. That is, the blood sample is conventionally collected in an evacuated container, and separation of the serum from the whole cells may be achieved by centrifuging the sample within that container, or within another container to which the sample has been transferred. Thereafter, the serum is commonly poured off into yet another container for the desired clinical testing. All such transfer operations are time consuming, requiring either hand processing or complicated, expensive automatic handling. Furthermore, whenever there is a transfer of a liquid sample to a separate, open container, the sample is aerated and CO.sub.2 loss or gain can occur. There is also the danger of improper transfer, either by the use of the wrong container, by the improper patient labeling of the new container, or by both. Still further, contamination of the serum by foreign materials or infection of the operator can occur. Reuse of the same dispensing device for sequential samples requires careful sterilization to avoid contamination. Thus, a system which keeps the blood sample confined to essentially one container from its collection to the actual dispensing for analysis is a distinct, sought-after improvement.
At the centrifuging stage, a variety of means have been provided for more or less plugging the serum-cell interface that is formed during centrifuging, whereby remixing of the cells and serum is prevented. U.S. Pat. Nos. 3,647,070; 3,779,383; 3,780,935; 3,800,947; 3,849,072 and 3,850,174 are representative of devices of this nature. The disclosures of U.S. Pat. Nos. 3,647,070; 3,779,383; 3,800,947 and 3,849,072 are typical of mechanical valve devices which prevent flow across the interface. Such devices, however, are quite complicated, resulting in increased cost of manufacture. Furthermore, they are susceptible to mechanical failure and do not automatically seek out the serum-cell interface. Devices such as are shown in U.S. Pat. No. 3,779,383 are not provided with valve means at the serum end to permit ready removal of the serum. Instead, the plug must be removed and the serum either poured off, as by tilting the container, or it must be aspirated or otherwise drawn off.
Of the many devices available to provide blood serum for analysis, the one which has become the norm is the evacuated container. This is simply a partially evacuated glass tube open at one end except for a septum placed there. One improvement over such an evacuated container which is particularly useful comprises a glass tube open only at one end, a septum affixed to that end when the tube is evacuated, and a movable plug contained within the tube. The plug is preferably a silica gel, with or without a plastic cup-like mandrel positioned with its open end pointed to the septum. By reason of the vacuum, collected blood is easily drawn into the container. The container is then spun about a centrifuge axis adjacent to the septum end, and the gel by reason of its selected specific gravity works up to the serum-cell interface where it plugs the container against remixing of the serum and cells. An example of such a container but without the mandrel is shown in U.S. Pat. No. 3,852,194.
Although such a device is useful in separating the serum from the cells, it has not avoided the transfer difficulties noted above. Furthermore, by pouring out the serum through the theretofore septum-plugged end, it is possible to contaminate the serum with blood cells which collected at the septum-container interface prior to centrifuging, a condition known as "blood-ring contamination".
Other patents relating to blood serum separation in general are U.S. Pat. Nos. 3,645,253; 3,687,296; 3,706,305; 3,706,306; and 3,771,965. Some of these, while not relying on a plug to provide a barrier between serum and cells, use a filter to separate serum from the blood cells.